Ford’s 3rd generation powersplit hybrid system
24 February 2012
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| Output from Self-Organizing Map of attributes and component sizing. Each pixel in each 3d contour represents a design which plots an attribute against a design feature or a design feature against another design feature to identify optimum combinations to deliver desired effects. This is a very important tool for Ford, Gray said. Click to enlarge. |
The hybrid system in the coming 2013 MY Fusion and C-Max hybrid electric vehicles (HEVs) (earlier post) marks the third major generation of Ford’s powersplit system. The overall system sizing and all major components were optimized for class-leading efficiency, with each major subsystem and many new components being redesigned to deliver the gains, said Chuck Gray, Chief Engineer - Ford Electrification Engineering, at the SAE Hybrid Vehicle Technologies Symposium this week in San Diego.
With the Generation 3 HEV system, Ford decided to downsize the engine from a 2.5L Atkinson to a 2.0L Atkinson to improve fuel economy. This, noted Gray, results in a reduction in acceleration and vehicle speed. However, Ford was able to compensate for that reduction by increasing battery power with its new Li-ion pack (earlier post), and increased electric power through the motor and the generator to recover to nearly the same level of performance as the outgoing model, but with significantly improved fuel economy. In-house engineering was a key enabler and included all controls, the battery pack, transmission and eDrive system, Gray said.
With the final system, Ford was able to deliver 140 kW of power from a combined engine peak power of 105 kW and its new 35 kW battery. The 2012 Fusion Hybrid carries an EPA fuel economy rating of 41 mpg city, 36 mpg highway; Ford expects the upcoming 2013 Fusion Hybrid to offer about 47 mpg city, 44 mpg highway.
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| Rough schematic of Ford’s powersplit architecture. Click to enlarge. |
Powersplit architecture. Ford has been working on its powersplit system for more than 8 years, and more than 10 years, counting early development, Gray said. The powersplit system consists of two electric machines connected to the engine and wheels through a single planetary gear set. Engine power is split between mechanical and electrical paths; E-CVT functionality is delivered through generator speed control.
It’s a simple mechanical arrangement, Gray said, noting that there are no clutches, and no torque converter. The e-CVTs functions to operate either power source in the optimum arrangement. The hybrid system offers four modes of operation:
- Electric drive.
- Engine drive - positive split.
- Engine drive - negative split.
- Regenerative braking.
One of the outcomes of the redesigned system is reduced engine runtime; in the third-generation system, Ford was able to reduce engine runtime by up to 30%. Additionally, the extra capability of the e-Drive increased the all-electric speed range up to 62 mph. All of that contributes to the overall fuel economy improvement, Gray noted.
Ford was also able to improve the brake specific fuel consumption of the 2.0-liter engine over the 2.5-liter engine from 0-10% in the main regions where they operate. On a plot of break specific fuel consumption vs. output power, the 2.0-liter Atkinson shows about a 3% improvement in the primary real-world operating region compared to its 2.5-liter predecessor.
With the e-Drive system—the inverter, controls and electric machines—Ford engineers were able to deliver measurable loss improvements of up to 4.5% over three different operating points, due to the attention to detail in design and the controls, Gray said.
The battery itself is another whole conundrum...various considerations to be pondered are size, location, thermal management, type of cell, type of chemistry, how control it, how much power, what’s the SOC and so on—a whole multitude of decisions.
—Chuck Gray
The new battery pack, designed and built by Ford using prismatic Li-ion cells from Panasonic, has a charge and discharge power of 35 kW and nearly double the specific power per unit mass of the outgoing NiMH product (0.84 kW/kg vs. 0.47 kW/kg). The pack is cabin air cooled and packaged in a similar location to its predecessor.
Ford also redesigned the Fusion top hat with an eyer to improving aerodynamics; the 2013 Fusion Hybrid offers a 10-15% drag reduction form the outgoing product due to body design as well as the addition of features such as a full active grill.
Toyota and Hyundai may have to upgrade their HEVs to keep up with Ford's?
Competition will bring 60+ mpg NEVs to the market soon.
Posted by: HarveyD | 24 February 2012 at 01:32 PM
I don't know, Harvey.
Compare the current Ford Fusion hybrid to the 2011 Toyota Camry hybrid. The Fusion hybrid offers better fuel economy, but at a pretty significant price premium.
Additionally, when Consumer Reports tesed the Fusion hybrid in real world driving, they achieved fuel economy similar to that of the Camry hybrid -- making that premium seem even bigger.
The 2012 Camry hybrid, based on early world from Ford regarding Fusion pricing, will probably again be significantly cheaper than the 2013 Fusion hybrid. Plus, even though the Fusion hybrid will be more fuel efficient according to the EPA, will it be in the real world?
Besides, I don't think fuel economy is really the bar, it's cost-effectiveness. Thus far the Camry hybrid has been more cost-effective in the real world.
So until Ford starts selling more cost-effective hybrids than Toyota, I don't think Toyota has much to worry about. Only cost-effectiveness can really drive sales.
Posted by: Chad Snyder | 24 February 2012 at 01:50 PM
Which ever one produces the first AWD hybrid will get my money.
Wish they would hurry up.
Posted by: Lucas | 24 February 2012 at 03:50 PM
Lucas...those vehicles already exist:
a. VW Toureq Hybrid
b. Ford Escape Hybrid
c. Toyota Highlander Hybrid
d. Toyota Lexus 450 Hybrid
e. GMC Sierra 1500 Hybrid
g. Chevy Tahoe Hybrid
Have your pick among above.
Toyota will soon have a few more choices:
a. RAV-4 Hybrid
b. Venza Hybrid
c. Matrix Hybrid
d. Kluger Hybrid.
e. Sienna Hybrid.
Posted by: HarveyD | 24 February 2012 at 05:08 PM
It’s a simple mechanical arrangement, Gray said
I can not count the number of times I have pointed that out to people. Many seem to automatically assume a hybrid is complex. The contrary is true, it is mechanically simple and I can safely say that a Prius and comparable hybrids like the Fusion will have the closest thing resembling an eternal life.
Posted by: Arne | 25 February 2012 at 01:53 AM
The main thing is that Ford are taking fuel economy and hybridisation seriously.
It really doesn't matter how you achieve it, as long as total oil usage stabilises (which may have already happened) and then reduces, without ruining the economy.
Posted by: mahonj | 25 February 2012 at 03:03 AM
I think many here are missing something...
I do not think this frames the question of is it Series or Parallel, but with the power split some new beast I will call adaptive? I look forward to the follow on "Energi" Drive.
Tangent to this is that no one is talking about or sees what will be the transmission-less drive motor in the Electric Focus unveiled at the 2010. After talking to one of the engineers @ the NAIAS, they are modulating torque via a controller. Is eliminating the Transmission a breakthrough that no one sees?
http://www.engadget.com/2011/01/11/ford-focus-electric-motor-extracted-split-asunder-coppery-guts/
If so why not build a rallye car or even sports cars with 2 of these motors, one front and one rear, on a Lotus Aluminum Chassis with their new 1.0 Litre 3 cylinder EcoBoost powering a motor and out "e-drive" the "Volt"?
IMHO as an observer of the company, they might have all the bits and pieces in their expanding parts bin to do it.
Even wilder, add Wesport's LPG Injectors for a non gasoline prime mover engine.
That might be one fine "Superleggera" sports car!
Posted by: EGeek | 25 February 2012 at 04:53 AM
@HarveyD:
I'm sorry to say, IMO, there is no good choice from your first list because:
- most (other than the long in the tooth Ford Escape that comes with prev. gen. technology and is flooding the N.Y. cab market) carry a much higher price than Camry hybrid/Fusion hybrid (the VW, starts from 62k+, mind you);
- none of them, if I'm not mistaken, would have a comparable fuel economy as that of the current Camry hybrid/Fusion hybrid.
So, why shouldn't Lucas just consider a fuel efficient AWD family vehicle in the market, say Subaru Legacy/Outback?
Posted by: Pierre | 25 February 2012 at 08:25 AM
Pierre - I could not have made a better response. I have been following Subaru for several years. If I had to buy right now, I would likely buy one of theirs.
I have a 1993 stretched Aerostar. It's still in good mechanical condition after 140,000 miles. All I have done to it is change the sparkplugs at 80K. About all I use it for now is camping.
The difference between its fuel use and all of them on the top list is most certainly not worth even considering a swap. In fact, By now, automakers should be selling AWD's that get 75 mpg - hybrid or not. A small, turbocharged Diesel can do that with a 2000 lb. vehicle today.
Where's it at ???
Posted by: Lucas | 25 February 2012 at 10:36 AM
Lucas...you may have to wait for an AWD BEV to get 75+ mpge.
If you're patient enough, it will be around sooner or latter.
Posted by: HarveyD | 25 February 2012 at 12:51 PM
Harvey - I believe you are right.
Posted by: Lucas | 25 February 2012 at 03:10 PM
Chad, FWIW, my colleague has an MKZ Hybrid and he gets 38 combined February through December and got around 36 mpg in January when we had "winter". So I don't know what your mpg would be but it would probably be better than Consumer Reports article that slammed it. It is a pretty nice car, the Fusion hybrid looks sharp inside and out but not as sharp as the MKZ.
Posted by: Ziv | 27 February 2012 at 09:55 AM